This invention relates generally to internal combustion engines, especially engines that power motor vehicles. More particularly the invention relates to an improvement in an automotive engine intake system for collecting certain hydrocarbon molecules that might otherwise escape to ambient atmosphere through the intake system when the engine is not running.
It is desirable to prevent escape of unburned hydrocarbons from a motor vehicle that is powered by an internal combustion engine. Evaporative emission controls are associated with the fuel storage systems of gasoline engines to collect fuel vapors that might otherwise escape to the surrounding environment. In such a system vapors are collected in a vapor collection canister that is periodically purged to combustion chambers of the engine when the engine is running in order to combust the collected vapors in the engine. Collected vapors may pass through a portion of an engine intake system, such as an intake manifold, or module, before entering the engine combustion chambers.
Accordingly, another potential source of escape for such vapors to the surrounding atmosphere is through the engine intake system. Certain systems are presently under consideration for collecting certain hydrocarbons in an engine intake system before they can escape to atmosphere. One such system utilizes a carbon-based collection medium that is fixed in place in the intake system. However, for that system to be efficient in collecting hydrocarbons, it may impose a potentially undesirable restriction to combustion airflow through the intake system when the engine is running. Another system is one that utilizes a power actuator, electric or pneumatic for example, to move the collector into the airflow passageway for use and to remove it for non-use. The latter system requires not only the collection medium, but also the addition of the actuator.
The compositions of petroleum-derived gasolines vary to some degree, but they include mainly hydrocarbon chains that include from five to more than 25 carbon atoms (mostly octane whose chemical symbol is C8H18). Certain blended gasolines also include some type of alcohol, ethanol for example, which is simply a hydrocarbon characterized by the presence of a hydroxyl group (xe2x80x94OH). Hydrocarbons like ethanol and octane are much heavier than air. Air consists approximately of 78.1% nitrogen (N2) and 20.9% oxygen (O2) per (dry) mole. Octane and ethanol are approximately 4.0 and 1.6 times as heavy as air respectively. When released in a vessel containing air, gaseous, heavier-than air, hydrocarbons like octane and ethanol will settle along the bottom of the vessel because of their relative weight, displacing some of the air from the vessel.
A preliminary novelty search in connection with this invention developed the following U.S. Pat. Nos. 3,368,326; 3,541,765; 3,572,013; 3,572,014; 3,747,303; and 4,279,630.
In general, those patents are illustrative of the use of activated carbon as an emission-control medium in association with an engine air cleaner that fits over and onto a carburetor, or throttle body, air inlet. Fuel vapors that may build up in the throat of the carburetor when the engine is not running will overflow the inlet and spill into the interior of the air cleaner housing. The vapors may be adsorbed by activated carbon present within the air cleaner housing, thereby preventing escape of adsorbed vapors to atmosphere. When the engine is running, the collected vapors may entrain with intake airflow to be subsequently combusted within the engine.
The present invention relates to novel engine intake systems, modules, and methods and involves the recognition that certain gaseous, heavier-than-air, hydrocarbons will fall to the lowest point of a vessel containing air to displace upwardly a similar volume of air. The invention embodies a geometry for an engine air intake system that provides a distinctive low feature, or pit, into which such hydrocarbons will fall and be collected so that their escape to the surrounding ambient atmosphere is avoided. A collection medium is disposed within the pit to collect the hydrocarbon vapors. By utilizing certain types of collection media, vapor collection may be encouraged by physical phenomena additional to collection by gravity. The use of activated carbon can aid collection by the presence of Van der Waals effect. While the gravity effect directs the hydrocarbons into the pit, the carbon itself attracts the molecules.
As such, the present invention is effective to capture certain hydrocarbon molecules that migrate upstream through an engine intake system when the engine is not running. One advantage of certain embodiments of the present invention is a reduction in hydrocarbon emissions without an accompanying restriction of airflow into the engine when running. Another advantage of certain embodiments is their inherent passivity, which does not require electrical or pneumatic connections, controls, or other devices for their effectiveness. Still another advantage is that vapor collection may be integrated with existing components, devices, and/or structures, such as a resonator for example, thereby making incorporation of the invention quite cost-efficient from the standpoint of both material usage and fabrication time.
Accordingly, one generic aspect of the invention relates to an engine intake system through which ambient air enters a combustion engine to be combusted with hydrocarbon fuel in combustion chamber space of the engine for running the engine. A walled main intake passageway has an upstream end communicated to ambient atmosphere and a downstream end communicated to the engine combustion chamber space. An imperforate walled pit encloses an interior space disposed at an elevation vertically below an imperforate wall of the main passageway. The pit has a first entrance communicating the interior space to ambient atmosphere and a second entrance communicating the interior space to the main intake passageway through the imperforate wall of the main passageway for enabling gaseous hydrocarbon that is heavier than air to fall into the interior space upon encountering the second entrance of the pit when migrating upstream within the main intake passageway toward the second entrance of the pit from the downstream end of the main passageway.
Another generic aspect relates to an engine intake system through which ambient air enters a combustion engine to be combusted with hydrocarbon fuel in combustion chamber space of the engine for running the engine. A walled main intake passageway has an upstream end communicated to ambient atmosphere and a downstream end communicated to the engine combustion chamber space. An imperforate walled pit encloses an interior space disposed at an elevation vertically below a bottom wall in the main passageway containing an entrance opening into the pit for enabling gaseous, heavier-than-air, hydrocarbon that is migrating upstream within the main intake passageway from the downstream end of the main passageway along the bottom wall toward the entrance opening to fall through the entrance opening into the pit upon encountering the entrance opening. A medium disposed within the interior space collects gaseous hydrocarbon that has fallen through the entrance opening into the pit.
Still another aspect relates to an engine intake system through which ambient air enters a combustion engine to be combusted with hydrocarbon fuel in combustion chamber space of the engine for running the engine. A walled main intake passageway has an upstream end communicated to ambient atmosphere and a downstream end communicated to the engine combustion chamber space. An imperforate walled resonator that is in communication with the main passageway tunes the intake system to the engine and includes an interior space disposed at an elevation vertically below a bottom wall in the main passageway containing an entrance opening into the interior space for enabling gaseous, heavier-than-air, hydrocarbon that migrates upstream within the main intake passageway from the downstream end of the main passageway along the bottom wall toward the entrance opening when the engine is not running to fall through the entrance opening into the interior space upon encountering the entrance opening. A medium disposed within the interior space collects gaseous hydrocarbon that has fallen through the entrance opening into the interior space.
Yet another generic aspect relates to an air intake module for a hydrocarbon-fueled combustion engine comprising a walled main intake passageway having an upstream end adapted to be communicated to ambient atmosphere and a downstream end adapted to be communicated to engine combustion chamber space. An imperforate walled pit that encloses an interior space is disposed at an elevation vertically below a bottom wall in the main passageway containing an entrance opening into the pit for enabling gaseous, heavier-than-air, hydrocarbon that migrates upstream within the main intake passageway from the downstream end of the main passageway along the bottom wall toward the entrance opening when the engine is not running to fall through the entrance opening into the pit upon encountering the entrance opening. A medium disposed within the interior space collects gaseous hydrocarbon that has fallen through the entrance opening into the pit.